Atrial Fibrillation (“AF”) is a rapid, highly irregular heartbeat caused by abnormalities in the electrical signals generated by the atria of the heart. AF is the most common cardiac arrhythmia and involves the two upper chambers of the heart. Surgical and catheter-based electrophysiology therapies have become common AF treatments throughout the world. Catheter ablation modifies the electrical pathways of the heart in order to treat the disease.
To measure electrical signals in the heart and assist the ablation operation, three catheters are inserted and guided to the left atrium. These three catheters include an ablation catheter, a circumferential mapping catheter, and a coronary sinus catheter. The operation is monitored with live fluoroscopic images for navigation guidance. Tracking three catheters with such different characteristics presents several challenges. Catheters have non-uniform appearance and shapes. In general, catheter characteristics include items such as tip electrode, size, spacing, and insertion length. Ablation catheters often have four electrodes with the tip electrode as a solid tube appearance in the fluoroscopic images, but may have electrode configuration different from each other. The circumferential mapping catheter has large intra-class variations because of differences in catheter diameter, electrode size, and number (i.e., number of poles and spacing). Coronary sinus catheters also vary from each other in terms of catheter length and electrode configuration. In addition, the three catheters may freely move within a large range and often occlude each other or other structures in the 2-D fluoroscopic images. During an electrophysiology operation such as an AF treatment, catheters may move into and out of an image. In addition, catheters are not rigid structures and may deform during the operation. Moreover, the use of fluoroscopic images presents additional challenges to tracking catheters in fluoroscopic images during the operation. Fluoroscopic images constantly change due to cardiac and respiratory motion and device movement. Additionally, structures in a fluoroscopic image often cause the background to be cluttered. The level of radiation may also affect the image quality and the signal to noise ratio.